The experimental program outlined in this proposal is designed to produce comprehensive, detailed information about the physical composition of the mitochondrial genome of Zea mays (corn or maize). This information will then be used by me and others to do future, in depth studies of mitochondrial gene function, including studies of RNA. DNA and protein biogenesis, regulation, interaction with the nuclear genome, development, inheritance, evolution, etc. Some information on all of these is likely to be developed during the present program. The physical composition of a small circular genome, such as mtDNA, is most easily visualized and used, and best approached in the form of a "map" of the genome. We hope to produce a map of mtDNA which contains an accurately ordered sequence for the fragments produced by several restriction endonucleases. We will thus divide the 50 micron genome into up to 100 or more discrete parts. The process of ordering will make use of safe E. coli/plasmid amplification of each fragment, thus giving us a complete "library" or "bank" of parts for future work. We will next determine the location of mt-rRNAs, mt-tRNAs and mt-mRNAs on the restriction map. A denaturation profile map, utilizing electron microscopy, will be used to assist ordering and to give further information on base composition of individual portions.